Measurement of the longitudinal bunch structure in the Photon Factory positron storage ring with a photon counting method

A photon counting system for measuring the time structure of bunches, such as the single-bunch impurity and the longitudinal distribution of electrons, was installed and has been improving in the KEK PF positron storage ring. Agreement between the experimental results concerning the rate of impurity growth and a calculation taking account of the relativistic effects of electron-electron scattering, which is the origin of the impurity growth, was fairly good. A deformation of the distribution at a high beam current was observed, and was analyzed phenomenologically.